In a conventional MIMO (Multiple-Input Multiple-Output) LTE system, each transmit signal stream is directly routed or mapped to a separate base station antenna, where all beam patterns overlap each other within a sector. Three examples are illustrated in FIGS. 1-3.
FIG. 1 shows a conventional 2T2R MIMO LTE base station system functional arrangement which includes a base station 30, a remote radio head 20, and a two element, +/−45° cross-polarized antenna 10a. In this 2T2R system, the antenna 10a generates two fixed, wide-angle overlapping beams 33a within a range or sector 32 for both the transmit and the receive functions. The base station 30 sends two transmit signal streams Tx1 and Tx2 to the remote head which, after some processing, routes each of those two transmit to a different corresponding antenna element within the cross-polarized antenna 10a for transmission over a corresponding one of the overlapping wide beams. On the receiver side, the remote radio head 20 receives and processes each of two signal streams Rx1 and Rx2 that are received by the two antenna elements and provides those two received signal streams to the base station 30.
FIG. 2 shows a conventional 2T4R MIMO LTE base station system functional arrangement which includes the base station 30, the remote radio head 20, and an antenna system 10b that includes two +/−45° cross-polarized antennas. In this 2T4R system, the antenna system 10b generates two fixed, wide-angle overlapping beams for the transmit function and four wide-angled overlapping beams for the receive function. The base station 30 sends two transmit signal streams Tx1 and Tx2 to the remote head 20 which forwards each transmit signal streams to a corresponding different one of the two antenna elements in one of the cross-polarized antennas 10b. On the receiver side, the remote radio head 20 receives and processes each of four signal streams Rx1, Rx2, Rx3, and Rx4 that are received by the two cross-polarized antenna elements and sends those received signals to the base station 30.
FIG. 3 shows a conventional 4T4R MIMO LTE base station system functional arrangement which includes the base station 30, the remote radio head 20, and the antenna system 10b that includes two +/−45° cross-polarized antennas. In this 4T4R system, the antenna system 10b generates four fixed, wide-angle overlapping beams for both the transmit function and the receive function. The base station 30 sends four transmit signal streams Tx1, Tx2, Tx3, and Tx4 to the remote head 20 which forwards each transmit signal to a corresponding different one of the four antenna elements. On the receiver side, the remote radio head 20 receives and processes each of four signal streams Rx1, Rx2, Rx3, and Rx4 that are received by the four antenna elements 10b and sends those four signals to the base station 30.